1. The problem is to solve the system by graphing the equation $y=3x-7$ and determine the number of solutions. 2. Since only one equation is given, the system is incomplete; a system requires at least two equations. 3. To solve a system by graphing, we need two or more equations to find their intersection. 4. Without a second equation, we cannot determine the number of solutions. 5. If you provide a second equation, I can graph both and find the solution. 6. For now, the graph of $y=3x-7$ is a straight line with slope 3 and y-intercept -7. 7. The line passes through points like $(0,-7)$ and $(1,-4)$. 8. Please provide the second equation to proceed with solving the system.